Starter having magnetic jaw advance



, INVENTORS. SAMUEL, GLB ARNOLD SCHI ATTORNE c Oct. 13, 1959 A. SC HIND EL ETAL STARTER HAVING MAGNETIC JAW ADVANCE Filed Feb. 27, 1958 United States Patent 2,'90s;1 70 STARTER HAVING MAGNETIC JA ADVANCE Arnold Schindel, Fair -Lawn,anjdSainnel Gilbert, Cedar Grove, -N .J.,-assignorsto Bendix Aviation Corporation, zUtica, N .Y., a corporation .of Delaware Application February 27,.1958, seria1 No. 117,871

6 Claims. (Gl. 74-'7) }tact the starter jaw. With current starting requirements .which call for cranking speeds up to ?-8-,000 r.p.m., the use of friction means for highspeed starter jaw engagement is not always dependable. lack of reliability -is due to limitations in the-materials which are used and the loss of friction due to wear of.parts of :the friction ;devices which impose the restraining'axial jforce.

An object of the present inventionris-to provide improved magnetic means arranged to ,cause the starter jaw aduancement.

.A :further object is 111.0 LPIOYid6"Sl-1Qh a tm-agnetic i jaw adyancingarrang ment .whereinztherestr n f vance diminishes'as the jaw teeth ;engage .:and the completion 30f engagement iisfie omplished hy;-the1inertial :eifects of ithe engine rotor.

- .Anotherobject is the provision .ofaispecific arrangernent of permanent magnetszon :the dtive;mernber and the starterljaw whichris easilydabricated-and assembled.

{Another objectis the provision ofsuch magnetic .jaw advance imeansrwherein there is adequate magnetic .at-

traction with variation :in-therestposition of athestarter jaw, and the starterjaw is held in retracted .positionafter zthestarting cycle.

. The accomplishment ,of :the aboveobjects, along with .the features and advantages 30f the :invention, will be apparent from the following .detailed .description and the accompanying drawing ,of an embodiment :of :the .in-

vention in which:

Fig. l is a longitudinal.cross sectional view of theijaw advancing section of a starter -anishows the starter jaw ;out of engagement with the engine jaw -and magnets between the starter ;.jaw and .a stationary support memher, and

Fig. 2 is an enlarged transverse cross-sectional view through the axial center of {the magnets and shows the relative circumferential positioningofthe magnets on the starterjaw and the inner stationary member and the.relative facing of the magnets .when the starter is at rest.

With reference to Fig. .1 .it -can be realized that, when starter v,drive member ,11 is caused to rotate by means of a clutch pack, planetary gearing .and a turbine (none of which is shown), drive member 11 will tend ,to rotate tubular starter jaw 13 with it due to the 'heliealspline connection unl ess.a radial restraint or normal force is imposed ,on the starter ,jaw. When such restr is imposed by magnetic means (described below), the starter jaw will advance axially by means of the extending and inclined faces. starter jaw-retraction is aided by-the magneticmeans/to be described and permits elimination of a spring which was previously used for this purpose and for the prehelical spline 15 on the drive member and the complepower tothe abovermentioned starter :turbine and hence the drive member ll can be air v:or combustion gases.

After'the starter bringsthegengineto starting-speed and the engine tends to drive .the starter, the vjaws will be conventionally separated due to'theconfiguration ofthe axial-extending jaw teeth .which havethe-usual axially- Full axial -separation or vention-of subsequentratchetting. j

The drive-member. '11 is rotatably mountedby ball bearing 3-1-0n amannular surface 33 of .a stationarysupport member 35 of the starter. :The stationary member 35 has an axial 'tubularextension 37 from surface 33. Within theicavity -of-:extension 37, :a-coil spring :39 is positioned and restrains resiliently.oneflangedend of a gages the engine-jawZS. It-is to be noted that the starter jaw 13 has a radially-extending flange 49 at z-itS 11111161 .end which is arranged to limit the axial :movement of the starter jaw 13 by1abntment ,with ,the helical spline of theaxially-stationary drivezmember 31 1.

With reference-to Figs.';l and 2, the above-mentioned magnetic means for providing restrain :on zthe starjter jaw 13 will now be described. A sleeve member 51 is .threaded on the extension :37 of the-stationary ,member 35 and is fixed thereon =-by dock :ring 53. The :end of ring 53 fits-in an axial-slotinendof extension :37. The

-sleeve 51 has four slots -55 -.in theinner ,end thereof with .inner open ends. [Four permanent magnets ;57 are positioned in slots 55. Each inner magnet 57 is encased by an insulating cup 59. FT-he inner ends. of the'magnets have an axially-extending, iinwardlydnclined projection .61 which is;used=to axially confinethemagnets. A'washer 63 has an annularindent-ationb-S arrangednto receive the projections61' of the magnets which project outiiror'n the-slots. A bearing retainerwasher't67 extends between positioning ring 63 and the-inner race of the bearing 31.

The threaded sleeve 551 does not contact positioning .washer 63 so that asmallgap'atthe radially-inneriloca- ,tion results. With this arrangement, the sleeve 51 axially positions and confines the structure which 1issinwardly thereof. Magnets 57'havea1ci-rcum-ferential length which vis equal to a thirty degree arc on i1th6ClICUI'H feI'eHCG .of sleeve 51 and are so constructed thatthe radially-outer surface of the magnets is the ,north pole-th ereof. The axial length of magnets :57 is abouttwice the length of axial travel of the starter jaw. V

The starter jaw 13 has an annular groove 71 in "the intermediate part .of its internal surface 73. Nine per- .manent magnets 75 having non-magnetic liners 76 at the bottom and radial-extending sides are uniformly spaced .in groove 71 against the inner shoulder thereof. Magnets 75 have radial key-stone sides and are spaced and .retainedradially by non-magnetic spacers 77 which have complementary radial sides .and are positioned between the :nine magnets. Asshown, .thetop one .of the spacers 77 is positioned as the final step by axially sliding it in cause separation and axial retraction begins.

slot 78 which'is the width of a spacer and extends 7 through an inclined face of a starter jaw tooth 19 to groove 71. It is apparent that, by rearrangement, the bottom surface of the groove could be extendedrtohthe outer-end of the starter jaw radially inward of the teeth tive to the starter jaw is prevented by the key 79 which is slid in keyway 80 in the starter jaw and groove 81 in the top spacer. The assembly of magnets and spacers "are restrained axially on the axially-extending surface of the groove 71 by split Washer 82 and a resilient split lock'ring 83 which abuts the axialouter shoulder of groove 71. The outer magnets 75 have their south poles at theradially-inwardface thereof, generally opposite the north poles of magnets 57, and have a circumferential length which is equal to about a thirty degree are on the circumference of the inner-surface of the'starter jaw 13. By reference to Fig. 2, it can be seen that two magnets .are in fullfacing relation and that major portions of the magnets will be in facing relation when there is rotation. The spacers 77 have an arc length of ten degrees. The spacers 77 are made of a cotton-phenol laminate. The non-magnetic cups 59 and liners 76 are made from a phenol-impregnated linen cloth which is about ten thousandths of an inch thick. These non-magnetic parts do not provide a good path for the magnetic flux to the adjacent steel parts. Magnets 57, 75 are made from a high-strength permanent magnetic material such as alnico #5 of the Crucible Steel Co. which consists of 8% aluminum, 14% nickel, 24% cobalt, 3% copper and remainder iron. It is to be noted that the faces of the magnets are closely spaced.

( .020") and that all magnets project from the mounting structure.

In operation, the starter will be energized and trans mittorque to the clutch barrel or drive member 11 which will tend to rotate the starter jaw 13 with it. Axial advancement of the starter jaw 13-for contact with the starter jaw 25 willbegin because of the strong magnetic attraction between the magnets 57 and 75 which have full-length opposite poles in substantial facing relation. It is who noted that, regardless of the slightly variable rotational position of the nine movable magnets 75 relative to the four stationary magnets 57 when the starter is at rest, there will be sufiicient magnetic attraction, due to major portions of the magnets being opposed, to impose restraint on the starter jaw so that it easily begins to advance axially by the looselyfitting helical spline 15, 17. Thereafter, the axial component of the normal force or restraint required for further jaw advancement will continue due to successive facing magnetic attractions during rotation. The completion of jaw engagement will be accomplished by the engine rotor inertial effects. At the time of full jaw tooth engagement, the magnetic attraction will besignificantly reduced. The reduced magnetic attraction results because the axial length of the magnets is such that upon. full engagement and lateral movement, there is no shearing of strong magnetic flux at about half of the faces of each set of magnets. In this manner, heat generation is reduced under the high-speed cranking conditions. It is to be noted that the geometry of the magnets is such that lateral motion of the starter jaw is impeded but slightly, 'resulting'in rapid advance for small rotation 'and thereby minimizing engagement shock.

When the engine speed slightly exceeds the starter speed, the forces on the inclined faces of the jaws will Further retraction of starter jaw over the helical connection, as the drive member is coasting to rest after the starting power is cut off at engine startingspeed, will be aided by the magnetic attraction existing after initial axial re- 1. In a starter having an engine jaw and tracting movement of the starter jaw. After the starter by a helical spline connection for axial advancement and retraction, the improvementcomprising starter jaw magnetic means on said starter jaw, stationary magnetic means opposed to said starter jaw magnetic means and radially-spaced closely to said'starter jaw magnetic means, the facing end of said starter jaw magnetic means being.

of opposite polarity to the facing end of said stationary magnetic means, said starter jawmagnetic means and said stationary magnetic means being'so constructed and arranged that said-starter jaw is advanced due to re straint by magnetic. attraction between the magnetic means when said drive member is rotated. e

2. In a starter having an engine jaw and a starter jaw with the starter jaw being mounted. on a drive member by a helical spline connection for axial advancement and retraction, the improvement comprising a plurality of equi -spaced' starter jaw magnets mounted in a ring onsaid starter jaw, a plurality of equi-spaced' stationary magnets in a ring-opposed to said ring of starter jaw magnetsand-radially-spaced from said starter jaw magnets, the facing ends of saidstarter jaw magnets being-of opposite polarity to the facing ends of said stationary magnets, said. starter jaw magnets and said stationary magnets being so constructed and arranged that said starter jaw is advanced due to restraint by magnetic attraction between the rings of magnets when said drive member is rotated. a

3. In a starter having an engine jaw and a starter jaw with the starter jaw being mounted on a drive member by a helical spline connection for axial advancement and retraction, the improvement comprising a plurality of equi-spaced starter jaw magnets mounted in a ring on said starter jaw and projecting therefrom, a plurality of equi-spaced stationary magnets in a ring opposed to 'said ring of starter jaw magnets and radially-spaced inwardly fromsaid starter jaw magnets, the facing ends of said starter jaw magnets being of opposite polarity 'to the facing ends of said stationary magnets, said stationary magnets beingmountedin stationary member andprojecting therefrom, said magnets being of the same axial length so thatsignificantly less magnetic attraction is exerted between the magnets after initial advancement to jaw teeth engagement, wherebysaid starter jaw is advanced due torestraint by magnetic attraction between the rings of magnets andwhereby less shearing of strong magnetic flux occurs after full jaw engagement.

4. In a starter having an engine jaw and a starter jaw with the starter jaw being mounted on a drive member .by a helical spline connection for axial advancement and retraction, the improvement comprising 'a pluralityof equi-spaced starter jaw magnets mounted in a ringon said starter jaw' andhaving inner ends of one polarity, a

plurality of equi-spaced stationary magnets in a ring radisame and being about twice the travel distance of s'aid.

starter jaw so that significantly less magnetic attraction is exerted after initial jaw teeth engagement, whereby said starter jaw is initially advanced due to restraint by magnetic attraction among the magnets when said drive member is rotated and whereby said starter jaw is held in non-ratchetting position when the starter is not operating.

5. In a starter, the improved starter jaw advancing mechanism comprised of an engine jaw having an axiallyextending ring of teeth at one end which face the teeth of the starter jaw and are spaced slightly therefrom, said starter jaw having a helical spline on an intermediate part of its external surface, a drive barrel radially outward of said starter jaw and having, an internal helical spline engaging said starter jaw spline for starter jaw advancement into engagement with said engine jaw, said starter jaw having an internal annular surface terminated by an annular shoulder at the intermediate part thereof, an annular assembly of alternated starter jaw magnets and non-magnetic spacers abutting said shoulder, said magnets being shrouded by non-magnetic insulators at the bottom and transverse sides thereof, said magnets and spacers being of keystone transverse cross-section so that they are contained as a ring type structure, said starter jaw magnets at their radially-inward ends being of the same polarity, a stationary member having an annularsurfaced extension extending to within said starter jaw beyond the location of said assembly, a sleeve threaded on said extension and having a plurality of equi-spaced grooves at the inner end thereof, stationary permanent magnets in said grooves and projecting therefrom and shrouded by non-magnetic cups except for their radiallyouter faces, said stationary magnets having their radiallyinner faces facing said starter jaw magnets and being closely spaced thereto and of opposite polarity, the axialwidth of all of said magnets being about twice the travel distance of said starter jaw, said starter jaw magnets and said stationary magnets being so arranged that there are major portions of facing ends of said magnets in facing relation as said starter jaw is rotated, whereby said magnets exert a restraining force on said starter jaw to cause it to advance when the drive barrel is rotated and to cause it to remain retracted when said drive barrel is stationary and further whereby with full jaw engagement less magnetic flux is sheared adjacent the faces of the magnets.

6. In a starter, the improved starter jaw advancing mechanism comprised of an engine jaw having an axiallyextending ring of teeth, a tubular starter jaw having an axial-extending ring of teeth at one end which face the teeth of the engine jaw and are spaced slightly therefrom, said starter jaw having a helical spline on an intermediate part of its external surface, a drive barrel radially outward of said starter jaw and having an internal helical spline engaging said starter jaw spline for starter jaw advancement into engagement with said engine jaw, said tubular starter jaw having an internal annular surface terminated by an annular shoulder at the intermediate part thereof, an annular assembly of alternated starter jaw magnets and non-magnetic spacers abutting said shoulder, said magnets bein-g shrouded by non-magnetic insulators at the bottom and transverse sides thereof, said magnets and spacers being of keystone transverse cross-section so that they are contained as a ring type structure, means arranged so that one of said spacers is radially-outwardly key-fitted into said internal starter jaw surface to prevent rotation of the assembly relative to the starter jaw, means including a washer and lock ring arranged to axially restrain said assembly, said starter jaw magnets at their radially-inward ends being of the'same polarity, a stationary member having bearing means on a shoulder rotatably carrying said drive barrel and having an annularsurfaced extension of less diameter than said shoulder extending from said shoulder to within said starter jaw beyond the location of said assembly, a sleeve threaded on said extension and having a plurality of equi-spaced grooves at the inner end thereof, stationary permanent magnets in said grooves and projecting therefrom and shrouded by non-magnetic cups except for their radiallyouter faces, said magnets having inwardly-inclined projections extending axially out from the inner end of said sleeve, a washer on said extension having an annular indentation receiving the radially-inner part of said projections of said stationary magnets and axially restraining said stationary magnets, said stationary magnets having their radially-inner faces facing said starter jaw magnets and being closely spaced thereto and of opposite polarity, the axial-width of all of said magnets being about twice the travel distance of said starter jaw, said starter jaw magnets and said stationary magnets being so arranged that the facing end of one starter jaw magnet faces sub stantially the entire facing end of one of said stationary magnets when said starter jaw is in retracted position, whereby said magnets exert a restraining force on said starter jaw to cause it to advance when the drive barrel is rotated and to cause it to remain retracted when said drive barrel is stationary, and further whereby with full jaw engagement less magnetic flux is sheared adjacent the faces of the magnets.

References Cited in the file of this patent UNITED STATES PATENTS 2,437,871 Wood Mar. 16, 1948 2,578,094 Sears Dec. 11, 1951 2,665,674 Metsger et a1. Jan. 12, 1954. 

